Recently, there is an increasing demand for high output and small size of a drive motor which is mounted in a hybrid electric vehicle. Accordingly, a method of forming a coil by edgewise bending a flat rectangular conductor (wire) having a flat rectangular cross-section has been studied.
Patent Literature 1 discloses a technique for a rectangular coil, a rectangular coil manufacturing method, and a rectangular coil manufacturing apparatus.
According to this technique, when the flat rectangular conductor is to be edgewise bent, an inner periphery side of an edgewise bent portion of the flat rectangular conductor is limited in a thickness direction by use of a tool to prevent the edgewise bent portion from expanding or bulging.
When a flat rectangular conductor is edgewise bent, generally, an outer periphery side of an edgewise bent portion of the flat rectangular conductor becomes longer than an inner periphery side. This is because a force caused by an edgewise bending operation acts on the flat rectangular conductor to extend the outer periphery side of the flat rectangular conductor but compress the inner periphery side thereof.
Consequently, the flat rectangular conductor is likely to be formed in a shape having the edgewise bent portion in which the inner periphery side is thick and the outer periphery side thin. When the inner periphery side of the flat rectangular conductor becomes thick, generating outward bulging portions, the adjacent coils when mounted in the stator core will interfere with each other due to such bulging portions. When the coil formed of the flat rectangular conductor edgewise bent by this method is mounted in a stator core, the above shape is likely to deteriorate a space factor of a stator.
In Patent Literature 1, accordingly, the inner periphery side of the flat rectangular conductor is limited to a predetermined width during edgewise bending, thereby preventing the thickness of the edgewise bent portion of the flat rectangular conductor from increasing.
Patent Literature 2 discloses a technique for an edgewise winding method and apparatus. In this technique of the Patent Literature 2, as with Patent Literature 1, a tool including a press mechanism is used to press the inner periphery side of the edgewise bent portion in order to prevent the thickness of the edgewise bent portion of the flat rectangular conductor from increasing. Such pressurizing of the inner periphery side of the edgewise bent portion by the press mechanism through the tool during edgewise bending of the flat rectangular conductor prevents an increase in thickness of the edgewise bent portion of the flat rectangular conductor.